Control mechanism for fluid fuel burners



July 29, 1941. o. J. HOWARD :1- AL CONTROL MECHANISM FOR FLUID FUEL BURNERS Filed April 6, 1939 3 ShQGtS-Shefit 1 MN &

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and Samson J 195118 2 r" July 29, 1941. D. J. HOWARD ETAL 2,251,055

CONTROL MECHANISM FOR FLUID FUEL BURNERS I Filed April 6, 1939 3 Shets-Sheet 2 Inz fe rims ,Ua did I you/(1rd fiamsogw twn W firmin I n I 4, l WM... MI 1 3? y 29, 1941- D. J. HOWARD srm. 2,251,055

CONTROL MECHANISM FOR FLUID FUEL BURNERS Filed April 6, 1939 3 Sheets-Sheet 3 i Imfersfors 3021122 .1 JVm/ard 5611228022 [.[2 22.3012

Patented July 29, 1941 2,251,055 CONTROL MECHANISM FOR FLUID FUEL BUBNERS David J. Howard and Samson J.

cago, lll., assignors to Quaker Johnson, Chi- Manufacturing Company, Chicago, 111., a corporation of Illinois Application April 6, 1939, Serial No. 266,340

14 Claims.

This invention relates to certain new and useful improvements in control mechanism for fluid fuel burners, especially oil burners of the open pot type.

The invention provides improved mechanism for proportionately controlling, preferably in response to temperature changes in the space being heated by the burner, the flow of fuel and combustion air to the burner chamber. The fuel flows to the burner chamber through a pipe or passag provided with an adjustable valve mechanism adapted. even when the valve is given its maximum closing movement, to permit a minimum flow of fuel to the burner suflicient to maintain a pilot flame. This valve may be successively adjusted in the opening direction to provide the burner with fuel for a medium fire, or for a maximum or high fire. A suitable blower or fan forces air under pressure through a conduit to the burner chamber to provide the necessary combustion air for the medium or high fires. This air conduit is provided with an auxiliary opening in one of its walls through which air may be drawn in by natural draft to furnish combustion air for the pilot flame when the fuel flow is cut down to a minimum. This auxiliary opening in the air conduit is provided with a damper mechanism movable to open or close the natural-draft opening and, under certain conditions, to direct more or less of the air under pressure from the fan through a portion of the auxiliary opening so as to cut down the supply of pressure air to the burner. Preferably the blower will not be in operation when the oil supply is cut down to the minimum to provide the low or pilot-flame. Electrically actuated mechanism, preferably controlled from a room thermostat, functions to progressively open the fuel valve as the room temperature falls. Connections, preferably mechanical, are actuated by the valve adjusting mechanism to progressively adjust the damper mechanism so that the supply of combustion air to the burner will be properly proportioned to the fuel supply at all times. Preferably means is associated with the damper mechanism and operated by the pressure of air delivered from the blower to permit opening movement of the valve mechanism only when the blower is in operation, the fuel supply being automatically cut down to a minimum whenever the blower stops. This invention covers certain improvements on the control system disclosed and claimed in the copending application of which has matured into Patent 2,237,041 dated Apr. 1, 1941.

The principal object of this invention is to provide an improved control mechanism for fluid fuel burners as briefly described hereinabove and disclosed more in detail in the specifications which follow.

Another object is to provide improved means for proportionately adjusting the supply of fuel and combustion air to a hydrocarbon burner.

Another object is to provide improved means for controlling the air supply to a burner.

Another object is to provide improved means for selectively directing a portion or all of the flow of air from a continuously operating fan or blower to a burner.

Another object is to provide improved means for making the operation of a valve-opening mechanism dependent upon the flow of air from the blower.

Other objects and advantages of this invention will be more apparent from the following detailed description of one form of apparatus constructed and operating according to the principles of this invention.

In the accompanying drawings:

Fig. 1 is a side elevation of the complete burner assembly, the burner and a portion of the air-conduit being broken away in central vertical section.

Fig. 2 is a longitudinal vertical section through the damper-housing, this view being taken substantially on the line 2-2 of Fig. 3.

Fig. 3 is a horizontal section through the damper-housing taken substantially on the line 3-4 of Fig. 2.

Fig. 4 is a perspective view of the blower and control assembly shown at the left of Fig. 1.

Fig. 5 is a wiring diagram showing diagrammatically certain portions of the control mechanism.

Fig. 6 is a partial side elevation and partial central vertical section of the fuel-valve, the section being taken substantially on the line 6-6 of Fig. 5.

Fig. 7 is a wiring diagram similar to Fig. 5 but showing a modificatio The assembled apparatus as shown in Fig. 1 comprises the burner A adapted to be positioned within a furnace and connected by air conduit 13 with the fan or blower C and the assembly of controlling mechanism, indicated generally at D, positioned outside of the furnace. The mechanisms C and D are supported on a suitable Schreuder, Serial No. 219,269, filed July 14, 1938 base I carried by a plurality of adjustable supporting standards 2. The burner end of the assembly is supported by a standard 3 having a ball-joint connection with the base 4. By properly adjusting the supports 2, the assembly can be pivoted about the rocking support 3 so as to properly level the burner A.

The burner A as here shown is of known type comprising an inner flre-pot having an upright cylindrical side wall and a slightly concaved bottom 6 into which the fuel or oil is delivered from pipe I through inlet opening 3. The side walls of the pot I are provided with a plurality of air inlet openings 3 and II) to support the combustion. The air supplied through conduit B flows into the exterior casing I l around an intermediate shell l2 positioned between the inner and outer housings 5 and l l. The air flows from outer housing il through a large central opening l3 in the bottom of shell i2 and through a plurality of smaller openings l4 in the upper portion of shell l2 and thence through the pot openings 3 and III to support the combustion. The pot 5 is partially closed at the top by the annular baffle l5, and a pilot-ring or baffle I5 is positioned within the pot at an intermediate height, the ring 16 being supported on a plurality of inwardly projecting pins IT.

The flre is started by igniting the shallow pool of liquid fuel maintained on the bottom 6 of the pot by the restricted flow from pipe I, the heat thus created vaporizing sufficient of the fuel so that the flame will soon move up to the space directly beneath the pilot ring IS, the flame projecting upwardly through the central opening in this pilot ring but remaining entirely within the fire-pot. This is the low or pilot flame which continues as long as the fuel supply is cut down to a minimum. When the supply of fuel and air is increased to an intermediate stage so as to provide a larger fuel pool in the pot bottom and a proportionately increased air supply, the flame will move up above the pilot ring l6, and the combustion will take place partly above and partly below the upper fire-ring l5. When the supply of fuel and air is increased to the maximum for the high-fire, the flame will burn in and directly below the central opening in the firering l5 and extend above the pot into the combustion space thereover. This type of burner is now well known and forms no specific part of the present invention which is concerned primarily with improved means for controlling the flow of fuel and combustion air to the burner.

The air conduit B comprises a rectangular damper-casing l3 connected at its outlet end with the inlet end of the air tube I9 (see Fig. 2) the tube l9 extending through the furnace wall or door and being connected at its outlet end into the burner housing H (see Fig. l). The inlet end of casing I3 is connected by bolts 20 or other suitable means with the housing of blower C so that the open inlet end 2| of casing l3 will register with the discharge opening 22 of the blower casing,

The bottom wall of casing I8 is cut away to provide a large air opening divided into two similar passages 23 and 24 by the substantially balanced shutter 25 mounted intermediately on shaft 25 pivoted transversely across the central portion of the opening. When shutter 25 is in the closed position shown in solid lines in Fig. 2, both halves 23 and 24 of the bottom opening will be closed. Whenthe shutter is swung in a counterclockwise direction to the position indicated in dotted lines in Fig. 2, and in solid lines in Fig.

5, the openings or passages 23 and 24 will both be opened. The opening movement of shutter 25 is limited by the engagement of the upper wing 21 of the shutter with an adjustable screw 23 projecting down through the top wall of casing l8, or by any other suitable stop means. The upper wing 21 of the shutter is cut away or notched, as indicated at 23, so as to clear the oil pipe I which preferably is mounted longitudinally within the lower portion of the air conduit B. When the damper is moved to the horizontal or closed position, the cut-out portion 23 of the shutter is closed by a tongue 30 provided in the bottom wall of casing 13 (see Fig. 4). With the shutter 25 in its open position and before the fan or blower C is put in operation, air sumcient to support the burner at low or pilot flame is drawn by natural draft through the openings 23 and 24, and conduit B into the burner chamber.

The damper mechanism also includes a. vane or baiile member 3! carried by a shaft 32 pivoted transversely across the upper portion of casing I3 between the blower and shutter 25. When the blower is not in operation, the vane 3i will hang vertically, as shown in dotted lines Fig. 2. When the blower is operating, the air under pressure from the fan will swing the vane 3| to the inclinecl position shown in solid lines, Fig. 2. The vane 31 when in this position, will cooperate with the inclined shutter 25 to direct a large amount of the air under pressure from the fan through the bottom openings 23 and 24, thus cutting down the flow of air under pressure to the bumer A.

Means, hereinafter described in detail, is provided for progressively swinging shutter 25 in a clockwise direction from the open position shown in dotted lines (Fig. 2) to the closed position shown in solid lines as the oil supply to the burner is increased. As a result the lower wing 33 of shutter 25 will progressively close the opening 24 and at the same time the upper wing 21 of shutter 25 will close the other half 23 of the bottom opening so as to prevent the escape of pressureair through these openings and at the same time close the natural-draft inlet.

A mercury-tube switch 34 is suitably supported on one outer end of shaft 32 which carries the vane or baiile 3|. This switch 34 will normally be enclosed in a housing 35 removably supported at one side of damper casing I3 (see Fig. 4). When the blower is not in operation and vane 3| is hanging vertically, the tube of switch 34 will be so inclined that the contacts 36 and 31 in one end portion of the tube will not be engaged by the mercury globule 33 (Fig. 5). However, when the blower is operating and vane 3| is swung to the inclined position the switch tube will be tilted so that the mercury globule 33 will join the contacts 33 and 3'! and complete a control circuit (hereinafter described). The vane 3| may be notched or cut away, asindicated at 3| (Fig. 4) so as to clear the oil tube 1 when vane 3i swings to its vertical position.

The fan or blower C is preferably driven by the directly connected motor 39, the blower having an adjustable air intake at 4|). However, when air intake 40 has once been satisfactorily adjusted, this adjustment will not normally be disturbed and the fan will be driven at substantially constant speed. All changes in the flow of air from the blower to the burner are accomplished by adjusting the swinging shutter 25 controlling the auxiliary air openings 23 and 24.

Within the housing 48 supported on base I adjacent the blower C is a chamber containing a pool 01' oil or other liquid fuel maintained at a substantially constant level by a float-valve mechanism, as is well known in this art. Oil from this pool flows by gravity through the control valve E and pipe 42 to the outer inlet end of pipe I and thence through this pipe to the burner pot 5. Valve E is shown in dotted lines in Fig. 1, and more in detail in Figs. 5 and 6. The valve 13 comprises a tubular portion 48 which projects downwardly below the level of the oil pool 44 so that oil will tend to fiow through the opening 45 in tube 48. The valve stem 48 slidable in tube 45 is cut away at its lower end (Fig. 6) to provide a small upper slot 41 and a larger lower slot 41' extending through the lower end of the valve stem. When the valve stem is lowered to its extreme closed position, the small slot 41 will still register with opening 45 so as to permit a minimum flow of oil from pool 44 sufllcient to maintain the pilot fire in the burner. As the valve stem 48 is progressively elevated from this lowermost position, more and more of the larger slot 41' will be brought into registry with opening 45 so as to progressively increase the oil flow to the burner.

The inner diameter of tube 43 is increased at 48 to provide a housing for the spring 49 confined between the shoulder at the lower end oi recess 48 and a collar 58 adjacent the upper end of stem 48. Spring 48 constantly tends to open the va ve, the valve being held closed against spring #8 by the operating lever 5| pivoted at 52 and positioned in the housing 53 (Fig. 1) supported above the valve housing 4|. A pin 54 projecting laterally from valve stem 48 through a slot 55 in the upper portion of tube 43 is adapted to engage an adjustable stop-screw 56 to limit the opening movement of the valve. The closing movement of the valve is limited by the engagement of operating lever 5| with another stop-screw 51. It may here be noted that the valve operating and adjusting mechanism is, for the most part, shown diagrammatically in Fig. 5, and that actually the parts may be diiferently arranged and proportioned. A spring 58 normally swings the operating lever 5| in a clockwise direction so as to close the valve, and an adjusting screw 59 limits the opposite or counter-clockwise movement of lever 5|. A pair of suitable electrically operated motors F and G are utilized for swinging the main operating lever 5| against the resistance of spring 58 to open the valve E. In the form here shown the motor F comprises a bi-metallic strip I58 anchored at one end GI and adapted to warp or swing upwardly when heated by the passage of a suitable current through the heating coil 82. The free end of the bi-metallic strip 60 engages a projection 85 on lever 5| so as to swing lever 5| in a counter-clockwise or valve-opening direction until this movement is limited by the engagement of the bi-metallic strip 60 with an adjustable stop screw 54. This will permit the valve E to open until a small portion of the large slot 41' is in registry with opening 45 and a supply of oil sufficient to maintain an intermediate fire wil be permitted to flow to the burner A. The motor G is here shown as similar to the motor F. When the bi-metallic strip 65 is heated by coil 66 it will engage the projection 51 of lever 5| and swing the lever further in a counter-clockwise or valveopening direction. This will permit the valve to open to its maximum, this movement being limited by the engagement of pin 54 with the screw 56. A larger part of notch 41 in the valve stem will now be in registry with openings 45 and the flow or oil through the valve to the burner will be increased so as to maintain the maximum orhigh-fire.

A lever 88 intermediately pivoted at 88 has its longer arm connected through link 18 with the outer end or crank arm H secured on the outer end of shaft 28 which carries the shutter 25. A substantially vertically extending operating rod 12 projects adjacent its ends through the end portions of valveoperating lever 5| and the shorter arm 18 or damper-operating lever 58. The outer end 01' lever II is confined between a fixed stop collar I4 on rod 12 and a compression spring 15 surrounding the upper portion of rod I2 and confined between lever 5| and an adjusting nut 15 threaded on the upper end of the rod. The end 18 of damper-operating lever 88 is connected with rod 12 through a similar yieldable connection including the spring ll.

As the operating lever 5| is swung upwardly or in a counter-clockwise direction to permit the valve E to open, the lever will operate through spring 15 to lift the rod 12 and thereby move the lever system 58, M, II so as to swing the shutter 25 in a clockwise direction toward closed position. The operating arms of the lever system are so proportioned that the air flow to the burner will be increased or decreased in the desired proportion to the increase or decrease of the fuel flow caused by the adjustment of valve E. Preferably the parts are so proportioned that the shutter 25 will be completely closed before the valve E has reached its extreme open position, the final movement of lever 5| (after the shutter 25 is closed) slightly compressing the spring 15. As a consequence of this "over-travel of the operating lever 5|, on the return movement of lever 5|, the valveclosing adjustment will commence before the shutter 25 starts to open. Therefore the decrease in the air supply to the burner will be retarded with respect to the decrease in the fuel supply so that there will be ample air to complete the combustion of excess fuel already delivered to the pot and the pool in the pot bottom will be reduced in size to the amount required for the lower flame before the air flow is cut down proportionately.

Referring again to the wiring diagram of Fig. 5, at 18 and I8 are shown the wires of a main power supply circuit. This power supply may be cut of! by opening the main switch 80. The primary coil 8| of a transformer T is connected through leads 82 and 83 across the respective power mains l8 and 18. The secondary 84 of transformer T supplies low voltage current to the control devices hereinafter described.

The thermostat H is suitably positioned to respond to temperature changes in the room or space that is being heated by the burner A. The thermostatic member 85 will function, as the temperature falls, to successively move the arm 88 into engagement with the fixed contacts 81 and 88. One wire of the control circuits is permanently connected to the movable thermostatic member at 88. Assuming that the temperature has fallen to the point where thermostat contact 88 engages the fixed contact 81, a control circuit will be completed as follows: From the secondary 84 of transformer T through wire 98, thermostat contacts 86 d 8 wire 8|, heater coil 92, and wires 83 and 84 back to the transformer-secondary 84. The heater 8! is part of a relay assembly K also comprising a bi-metallic strip anchored at one end 88 and connected at its movable end through link 81 with the pivoted mercury switch 90. when heating coil 02 is energized, the bimetallic strip 05 will warp upwardly so as to lift link 01 and tilt the switch 00 so that the mercury globule will complete a circuit through the switch contacts 00 and I00. A fan-energizing circuit will now be completed as follows: From power main through wire l0l, fan-motor 30, wire I02. switch contacts 90 and I00 and wire I00 to the other power main 10. The fan or blower will now run continuously as long as the first mentioned control circuit is completed through thermostat H.

As soon as the blower 0 starts to operate, the hanging vane or baflie 3| will be swung to its inclined position so as to close the mercury switch 30, and this switch will remain closed as long and only as long as the blower C continues to operate. An energizing circuit for valve-operating motor F is now completed as follows: From the transformer through wire 90, thermostat contacts 00 and 01, wires 0| and I04, heating coil 02, wire I05, switch 34 and wire 94 back to the transformer. Motor F will now act to swing the lever El and permit valve E to open to its in.-

termediate position. At the same time the mechanical lever connections will be actuated to partially close the shutter 25.

If there is a further drop in room temperature the thermostat 1-1 will cause arm 80 to contact with the second terminal 00 of the thermostat. An energizing circuit for valve-opening motor G will now be completed as follows: From the transformer through wire 00, thermostat contacts 08 and 00, wire I00, heating coil 00, wire II" to wire I05 and thence, as before, through switch 00 back to the transformer. The motor G will now swing lever ill to its limit in the counterclockwise direction and permit the valve E to fully open. At the same time the previously described mechanical connections will completely close the shutter 20.

As the temperature within the heated space rises, the thermostat arm 00 will swing in the opposite direction and the contact 08 will first be disengaged so as to break the last-described energizing circuit for motor G. The spring 58 will now swing lever 5| clockwise to partially close valve E to its intermediate position. At the same time shutter will be partially opened. If the rise in temperature is suificient to cause thermostat H to break the connection between terminals 06 and 01, the energizing circuits for heat-motor F and relay K will both be broken. The valve E will now be moved to its closed position, that is only the minimum flow of oil sufficient to maintain the pilot-flame will be permitted. At the same time the blower C will cease to operate and shutter 25 will be moved to its most open position so that a free flow of air is admitted under natural draft through opening 23 to supply suiiflcient combustion air for the pilot-flame.

If at any time (regardless of temperature conditions and the positioning of thermostat H) the blower C should cease to operate either through breaking of the motor circuit or for any other reason, the vane 3| will swing back to its vertical position so as to open the switch 0|. In that event both valve-opening circuits will be broken, or it will be impossible to complete these circuits at the thermostat H, and the valve E will be automatically closed so as to cut down the flow of oil to a minimum. At them time shutter 25 will be opened and since the minimum of oil can be adequately burned by the air flowing in through 0 under natural draft. there wm be no t... ation of oil or fuel in the burner, except thhmalkpool to maintain the pilot-flame. Only this low fire can be maintained until the blower C is again able to function. I

In the simplified system indicated in Fig. '7. the blower-motor I0 is not controlled by thermostat H but is connected permanently across the power mains I0 and 10 through wires I00 and I00. The blower will operate continuously as long as the main switch 80 is closed. The relay K and the control circuit first described are omitted entirely, otherwise the operating connections are the same as described in connection with Fig. 5. As in the first described system, the valve-opening circuits cannot be completed unless the blower is functioning to swing vane 0| and maintain switch 0! closed. The only difference in operation is that the blower runs continuously, even when the burner is on low fire, that is only the pilot is burning. At this time the excessive air from the blower will be dissipated through opening 24 in the bottom of damper-casing I0.

We claim: v

1. In combination, a burner, means for delivering a fluid fuel to'the burner, means for supplying combustion air to the burner including a blower and an air conduit leading from the blower to the burner. there being an auxiliary opening in a wall of the conduit between the blower and burner for admitting air under natural draft when the blower is not operating and permitting the escape of air under pressure from the blower, movable damper means for increasing or decreasing the effective size of said opening for controlling the flow of air to the burner, and electrically actuated motor means controlled by temperature changes in the space heated by the burner for moving the damper means to selected positions.

2. In combination, a burner, means for delivering a fluid fuel to the burner, means for supplying combustion air to the burner including a blower and an air conduit leading from the blower to the burner, there being an auxiliary opening in a wall of the conduit between the blower and burner, damper-means comprising a shutter intermediately pivoted acrm a central portion of said opening, said shutter when in open position directing air under pressure from the blower through the opening and admitting air under natural draft through the opening when the blower is not in operation. and when in closed position closing the opening, and electrically actuated motor means controlled by temperature changes in the space heated by the burner for moving the damper means to selected positions.

3. In combination, a burner, means for delivering a fluid fuel to the burner, means for supplying combustion air to the burner including a blower and an air conduit leading from the blower to the burner, there being an auxiliary opening in a wall of the conduit between the blower and burner, damper-means comprising a shutter intermediately pivoted to control the effective size of said opening, said shutter when in open position directing air under pressure from the blower through the opening and admitting air under natural draft through the opening when 'the blower is not in operation, and when in closed flow position closing the opening, said damper-means also comprising a pivoted vane extending transverselyi of the conduit between the blower and shutter when the blower is not in operation, and being moved by air under pressure from the blower to a position where it cooperates with the open shutter to direct air from the blower through the opening. and means for moving the shutter to or from closed position.

4. In combination, a burner, valve-means for controlling the flow of fuel to the burner, damper-means for controlling the flow of air to the burner, thermostatically controlled means for adjusting the valve means, and mechanical connections between the valve-actuating means and the damper-means for adiusting the damper means as the valve is opened or closed to proportionately increase or decrease the flow of fuel and air to the burner, said mechanical connections comprising a spring means that is compressed by an additional valve-opening movement after the air-increasing damper adjustment is completed, said spring causing an initial valve-closing move ment before the air-decreasing damper adjustment begins.

5. In combination, a burner, means for delivering a fluid fuel to the burner, valve-means controlling the flow of fuel to the burner, means for supplying combustion air to the burner including a blower and an air conduit leading from the blower to the burner, there being an auxiliary opening in a wall of the conduit between the blower and burner for admitting air under natural-draft and permitting the escape of air under pressure from the blower, normally-open damper means for controlling the effective size of said opening and directing the flow of air through the opening, and motor means including interconnecting means between the valvemeans and damper means for substantially simultaneously adjusting said valve-means to increase the fuel flow and adjusting said damper means toward closed position to increase the air flow to the burner.

6. In combination, a burner, means for delivering a fluid fuel to the burner, valve-means controlling the i'low of fuel to the burner, means for supplying combustion air to the burner including a blower and an air conduit leading from the blower to the burner, there being an auxiliary opening in a wall of the conduit between the blower and burner for admitting air under natural-draft and permitting the escape of air under pressure from the blower, normally-open damper means for controlling the effective size of said opening and directing the flow of air through the opening, and motor means responsive to temperature changes in the space heated by the burner and including interconnecting means between the valve-means and damper means for substantially simultaneously adjusting said valve means to increase the fuel flow and adjusting said damper means toward closed position to increase the air flow to the burner.

7. In combination, a burner, means for delivering a fluid fuel to the burner, Valve-means controlling the flow of fuel to the burner, means for supplying combustion air to the burner including a blower and an air conduit leading from the blower to the burner, there being an auxiliary opening in a wall of the conduit between the blower and burner for admitting air under natural-draft and permitting the escape of air under pressure from the blower, normally-open damper means for controlling the effective size of said opening and directing the flow of air through the opening. thermostatically controlled means for adJusting said valvemeans, and mechanical connections between the valve-actuah ing means and the damper-means for closing the damper-means as the valve is opened, or vice versa, to proportionally increase or decrease the flow of fuel and air to the burner. V

8. In combination, a burner, means for delivering a fluid fuel to the burner, valve-means controlling the flow of fuel to the burner, means for supplying combustion air to the burner including a blower and an air conduit leading from the blower to the burner, there 'being an auxiliary opening in a wall of the conduit between the blower and burner for admitting air under natural-draft and permitting the escape of air under pressure from the blower, normally-open damper means for controlling the effective size of said opening and directing the flow of air through the opening, thermostatically controlled means for adjusting said valve-means, mechanical connections between the valve-actuating means and the damper-means for closing the damper-means as the valve is opened, or vice versa, to proportionally increase or decrease the flow of fuel and air to the burner, said mechanical connections comprising a spring means for permitting an additional valve-opening movement after the damper is completely closed, and causing an initial valve-closing movement before the opening movement of the damper begins.

9. In combination, a burner, means for delivering a fluid fuel to the burner, valve-means controlling the fiow of fuel to the burner, means for supplying combustion air to the burner including a blower and an air conduit leading from the blower to the burner, there being an auxiliary opening in a wall of the conduit between the blower and burner for admitting air under natural-draft and permitting the escape of air under pressure from the blower, normally-open damper means for controlling the effective size of said opening and directing the flow of air through the opening, thermostatically controlled means for adjusting said valve-means, mechanical connections between the valve-actuating means and the damper-means for closing the damper-means as the valve is opened, or vice versa, to proportionately increase or decrease the flow of fuel and air to the burner, and means for causing the valve-means to reduce the fuel flow to a minimum when the blower ceases to function.

10. In combination, a burner, means for delivering a fluid fuel to the burner, valve-means controlling the flow of fuel to the burner, means for supplying combustion air to the burner including a blower and an air conduit leading from the blower to the burner, there being an auxiliary opening in a wall of the conduit between the blower and burner, a shutter intermediately pivoted across a central portion of the opening, said shutter when in open position directing air under pressure from the blower through the opening before reaching the burner and admitting air under natural-draft through the opening when the blower is not operating, and when in closed position closing the opening, and means for substantially simultaneously adjusting said valvemeans toward or from a fully open position and adjusting said shutter toward or from a fully closed position to proportionately increase or decrease the flow of fuel and air to the burner.

11. In combination, a burner, means for supplying a fluid fuel to the burner, valve means for normally limiting the flow of fuel to the burner, means including an electric circuit and a pair of switches therein for controllably opening said valve-means to increase this fuel flow, means for supplying combustion air to the burner including a blower and a conduit for carrying the air stream from the blower to the burner. movable damper-means positioned in the conduit in the path oi the air stream, thermostatic means for opening and closing one of the switches, and connections between the damper-means and the second switch for closing the second switch by movement of the damper means caused by the air stream and rendering the valve-opening means operable only while the blower is operating to product the air stream.

12. In combination, a burner, means for delivering a fluid fuel to the burner, valve-means controlling the flow of fuel to the burner, means for supplying combustion air to the burner including a blower and an air conduit leading from the blower to the burner, there being an auxiliary opening in a wall of the conduit between the blower and burner, a movable shutter controlling the eflective size of the opening, said shutter when in open position directing air under pressure from the blower through the opening and admitting air under natural-draft through the opening when the blower is not operating, and when in closed position closing the opening, a pivoted vane extending transversely of the conduit between the blower and shutter when the blower is not in operation, and being swung by air under pressure from the blower to a position where it cooperates with the open shutter to direct air from the blower through the opening, means comprising a thermostatically controlled circuit for adjusting said valve-means, mechanical connections between the valve-actuating means and the shutter for closing the shutter as the valve is opened, or vice versa, to proportionately increase or decrease the flow of fuel and air to the burner, and a switch in said valve-controlling circuit. said switch being operatively connected with the vane so that the switch will be closed when the blower is functioning and open when the blower is not functioning.

13. In combination, a burner, means for delivering a fluid fuel to the burner, valve-means controlling the flow of fuel supplying combustion air to the burner including a blower and an air conduit leading from the blower to the burner, there being an auxiliary opening in a wall of the conduit between the 5 to the burner, means for o blower and burner, a movable shutter controlling the eifective size of the opening, said shutter when in open position directing air under pressure from the blower through the opening and admitting air under natural-draft through the opening when the blower is not operating, and when in closed position closing the opening, a pivoted vane extending transversely of the conduit between the blower and shutter when the blower is not in operation, and being swung by air under pressure from the blower to a position where it cooperates with the open shutter to direct air from the blower through the opening, a thermostat responsive to changes in room temperature, means comprising an electric circuit closed by the thermostat at a predetermined temperature for starting the blower, means comprising a second circuit also closed by the thermostat for adjusting the valvemeans to increase the flow of fuel to the burner, a switch in said second circuit operated by the vane so that the switch is only closed while the blower is functioning, and mechanical connections between the valve-actuating means and the shutter for closing the shutter as the valve is opened, or vice versa.

14. In combination, a burner, means for delivering a fluid fuel to the burner, means for supplying combustion air to the burner including a blower and an air conduit leading from the blower to the burner, there being an 'auxiliary opening in a wall of the conduit between the blower and burner, damper-means comprising a shutter intermediately pivoted to control the effective size of said opening, said shutter when in open position directing air under pressure from the blower through the opening and admitting air under natural draft through the opening when the blower is not in operation, and when in closed position closing the opening, said damper-means also comprising a pivoted vane extending transversely of the conduit between the blower and shutter when the blower is not in operation, and being moved by air under pressure from the blower to a position where it cooperates with the open shutter to direct air from the blower through the opening, and means responsive to temperature changes in the space heated by the burner for moving the shutter to or from closed position and simultaneously controlling the rate of fuel supply to the burner, said means including a switch operated by the pivoted vane.

DAVID J. HOWARD. SAMSON J. JOHNSON.

CERTIFICATE OF CORRECTION.

Patent No. 2,251,055. July 29, 191d.

DAVID J. HOWARD, 'ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correctiona s follows} Page 6, first column, line 17, claim 11, for the Word "product" read --produoe--; nd that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Offic Signed and sealed this 23rd day of September, A. D. 1941.

Henry Van Arsdale (Seal) Acting Commissioner of Patents. 

